Core drill



Oct. 18, 1932. 4 c, ALLEN 1,883,321

GORE DRILL Filed July so, 1928 Evy. 1.

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Patented Oct. 18, 1932 UNITED STATES PATENT OFFICE MORRIS C. ALLEN, OF CHICAGO, ILLINOIS, ASSIGNOR TO SULLIVAN MACHINERY COMPANY, A CORPORATION OF MASSACHUSETTS CORE DRILL Application fled July so,

This invention relates to core drills and more particularly to cutting bits for such drills.

Heretofore, especially in soft drilling, there has been a tendency for core drill bits of large diameter having a broad flat cutting surface to move laterally or wander out of alinement from the center of the hole at the bottom of the latter. This results in drilling a needlessly large hole and making the core very small or failing to make any core at all and has further resulted in a very severe carbon or diamond loss. I

An object of this invention is to provide an improved core drill bit so designed as to overcome the above disadvantages. A further object of this invention is to provide an improved core drill bit of the rotary diamond type having stepped cutting surfaces thereon thereby increasing the lateral diamond bearing surface and preventing lateral displacement of the bit in the hole, especially during soft cutting. A'still further object of this invention is to provide an improved core drill bit of the rotary diamond type having a large upper cu ting surface and a reduced bottom cutting surface thereon which increase the lateral bearing surface and centers the bit in alinement with the hole. A further object of this invention is to provide an improved core drill bit having stepped cutting surfaces and improved passage means for conducting fluid to the said cuttin sur- .faces. These and other objects and a vantages of this invention will however hereinafter more fully appear.

In the accompanying drawing there is shown for purposes of illustration one form which the invention may assume in practice.

In this drawing,

Fig. 1 is a central longitudinal sectional view taken through the improved core drill, parts being shown in elevation.

Fi 2 is an end view of the improved cutting it.

Fi 3 is a detail view of the im roved bit showing the stepped cutting sur aces.

In this illustrative form of the invention there is shown a core barrel herein of the double tube type comprising an outer tube 1928. Serial 1T0. 286,215.

. 1 and a concentric inner core receiving tube 2, the inner and outer tubes herein referably being relatively rotatable. Threadedly connected at 3 to the lower end of the outer tube 1 is a bit 4 of improved design having a central opening 5 through which the core is adapted to pass as cutting progresses and 'an enlarged chamber 6. In this instance, formed at the bottom of the chamber 6 is an annular seat 7 which loosely receives the lower end of an annular core lifter ring or shell 8, the'core lifter ring being formed separate from the bit and spaced therefrom. The upper end of the core lifter ring 8 has a loose fit at 9 with the lower end of the core receiving tube 2. It will herein be noted that the core lifter ring 8 may freely rotate with the bit or remain stationary with the inner tube. As shown, the bit 4 is provided with lateral wings 10. Formed between the wings and connecting the chamber 6 with the bottom of the bit are series of holes 11, as clearly shown in Fig. 2. The core lifter ring 8 is provided with an internal tapered bore 12 which receives a usual tapered resilient split spring core lifter 13 of a well known form. In the improved design the bottom surfaces of the-wings 10 are cut away as at 14 thereby forming stepped cutting surfaces 15 and 16 within which the carbons or diamonds are set in the usual manner. These surfaces 15 and 16 taper downwardly and inwardly toward the core passage 5 and the center of the drill bit, the inner surface 15 being of the smaller diameter. Thus it will be noted that the improved bit provides wider diamond bearing surfaces on the bit and consequently prevents lateral movement thus tending to keep the drill bit always in alinement with the drill hole.

In the use of the improved core drill it will be noted that fluid flows from between the inner and outer tubes 2, 1 into the chamber 6 and flows through the series of holes 11 to the surfaces between the wings 10 and consequently washing the cuttings away from the stepped cutting surfaces 15, 16. It will be noted that no fluid is allowed to wash the core during drilling, the fluid flowing externally of the interior of the core receiving tube and bit to the bottom of the bit and is at no time in contact with the core. During the drilling operation the rotating bit 4 cuts a core which passes as drillin progresses through the core lifter 13 am into the inner core receiving tube 2, the latter normally remaining stationary with the core during rotation of the bit and consequently preventing the wearing away of the core', whlch in many instances is of relatively soft character, due to the contact of the core with some rotatin part.

As a result of e improvement it will be noted that there is provided an improved core bit of the rotary diamond type, especially adapted to use in soft material such as frequently encountered in oil well drilling, having stepped cutting surfaces of large cutting area which tend to keep the drill bit in alinement with the drill hole and which prevent excessive wear of the vdiamonds, the wearing down of the core as it passes into the core barrel and excessive enlargement of the drill hole such as would result from wandering of the bit. It will further be noted ly described one form which my invention may assume in practice, it will be understood that this form of the same is shown for purposes of illustration and that the invention may be modified and embodied in various other forms without departing from its spirit or the scope of the appended claims.

What I-claim as new and desire to secure by Letters Patent is:

1. In a core drill, an annular core cutting bit having a central core passage, said bit having guiding means comprising projections havin relatively wide -guiding surfaces and exten ing radially from said bit and spaced at intervals around the peripherythereof, said guiding means adapted to substantially fit and slidably engage the walls of the drill .hole to guide the bit during drilling, and

of the drill hole to guide the bit during drilling, the bottom faces of said projections be-' ing stepped to provide plane diamond receiving cutting surfaces 1n different lanes but conjointly extending from the e ge of the core passage to the outer periphery of the bit on the bottom faces of the projections for cutting out completely an annular kerf to admit said bit an to thereby form a. core, and the bottommost diamond receiving cutting surfaces being arranged closest to said core passage.

In testimony whereof I afix my si ature.

MORRIS C. N.

j ointlyextending from the edge of the core passage to the outer periphery of the bit on the bottom faces of the projections for cutting out completely an annular kerf to admit said bit and to thereby form a core.

2. In a core drill, an annular core cutting bit having a central core passage, said bit having 'guidin means comprising projections havin re tively wide guidin surfaces and exten radially from said bit and aced at intervals around the periphery t ereof, said means adapted to subshmtially and slidably engage the walls 

